Conventional air conditioning units include return air conditioning units that use return air, return/outside air conditioning units that use a combination of return and outside air and units that are dedicated to condition outside air only. A return air conditioning unit receives return air from a facility that the air conditioning unit is servicing. The return air is conditioned by passing through a cooling coil and supplied to the facility. In a return/outside air conditioning unit, the return air is typically mixed with the outside air before or after it passes through a cooling coil. On the other hand, a dedicated outside air conditioning unit receives outside air from the atmosphere and conditions it by passing through a cooling coil and thereby supplies conditioned air to the facility it is servicing.
In both conventional return/outside air conditioning units and dedicated outside air conditioning units, air enters through one side of a cooling coil and exits from the other side of the cooling coil in a single pass air flow configuration. However, because return air and outside air commonly have different properties, such as in humidity content and temperature, several differences between return air conditioning units and outside air conditioning units are prevalent. For example, because outside air may be warmer and more humid than return air, outside air conditioning units tend to pass air through cooling coils at a slower face velocity across the cooling coil than return/outside air conditioning units. Additionally, the cooling coil of a dedicated outside air conditioning unit may be sized differently than a return air conditioning unit. For instance, the cooling coil of an outside air conditioning unit will typically have a smaller surface area with more rows of coil in order to more efficiently cool the warmer outside air as it passes through the cooling coil system.
If an unmodified return/outside air conditioning unit were to be used to condition outside air, in order to reduce the temperature of the outside air to the desired air temperature, the face velocity at which the outside air would travel through the cooling coil would be a lot slower compared to the face velocity at which return air would travel through the cooling coil system. Because the velocity of the outside air travelling through the cooling coils is too slow, the cooling coils may freeze since heat is not being transferred from the outside air to the cooling coils fast enough to prevent the coil from freezing. For these reasons, utilizing conventional return/outside air conditioning units to condition outside air is not possible without enduring considerable expense for exchanging the cooling coils and/or the fan to prevent the cooling coils from freezing while adequately conditioning the outside air.
It is with respect to these considerations and others that the disclosure made herein are presented.